Cosmetic skincare serves primarily to strengthen or restore the natural function of the skin as a barrier against environmental influences (e.g. dirt, chemicals, microorganisms) and against the loss of substances intrinsic to the body (as well as water, also natural fats, electrolytes, etc.).
Impairment of this function may lead to increased resorption of toxic or allergenic substances or to attack by microorganisms, resulting in toxic or allergic skin reactions.
A further aim of skincare is to compensate for the loss by the skin of sebum and water caused by daily washing. This is particularly important when the natural regeneration ability is inadequate. Furthermore, skincare products should protect against environmental influences, in particular against sun and wind, and delay skin ageing.
Chronological skin ageing is caused, for example, by endogenous, genetically determined factors. As a result of ageing, the following structural damage and functional disorders, which can also fall under the term “senile xerosis”, arise in the epidermis and dermis:
a) dryness, roughness and formation of dryness wrinkles,
b) itching and
c) reduced refatting by sebaceous glands (e.g. after washing).
Exogenous factors, such as UV light and chemical noxae, can have a cumulative effect and, for example, accelerate or supplement the endogenous ageing processes. In the epidermis and dermis, for example, the following structural damage and functional disorders may arise in the skin in particular as a result of exogenous factors; these are more far-reaching than the degree and quality of the damage in the case of chronological ageing:
d) visible vascular dilations (teleangiectases, couperosis);
e) flaccidity and formation of wrinkles;
f) local hyperpigmentation, hypopigmentation and abnormal pigmentation (e.g. age spots) and
g) increased susceptibility to mechanical stress (e.g. cracking).